Ladders are well-known and useful implements. There are various types of ladders, including step ladders and extension ladders. While ladders are generally useful and convenient, they do suffer the disadvantage of being somewhat unstable, tending to tip laterally if a lateral force is applied thereto, particularly when the force is applied above the center of gravity of the ladder. As used herein, the term "lateral" refers to a direction or motion which is substantially parallel to the rungs or steps of a ladder. For example, a lateral adjustment would be one which is substantially parallel to the rungs or steps of the ladder. Also, ladders can possess a lack of transverse stability under certain circumstances. The term "transverse" herein refers to a direction which is substantially perpendicular to the rungs or steps of a ladder.
The present invention is directed to a method and apparatus for stabilizing a ladder, to minimize the unstableness which is characteristic of most commercial and non-commercial ladders.
Preferably, a ladder stabilizer will accommodate an uneven ground surface and will also allow an individual using a ladder to lean in various directions and move about without causing the ladder to sway or slip. It is also preferable that a ladder stabilizer be fully adjustable to accommodate other conditions such as the presence of a wall, tree, etc., while still rigidly and safely bracing the ladder.
Prior art ladder stabilizers generally do not provide sufficient adjustability and stability. For example U.S. Pat. No. 3,856,112, issued to A. H. Stewart, discloses a ladder stabilizer which basically includes a pair of slidably-connected elongate members, the uppermost of which is pivotally connected to the apex of a standard step ladder. While the stabilizer is apparently quite adjustable to accommodate various ground conditions, it is connected to the ladder at only one point. Such a "one point" connection technique generally does not provide a sufficiently rigid connection between the ladder and the stabilizer to securely brace the ladder against transverse and lateral disturbances. Thus, for example, if such a stabilizer was utilized and the ladder supplied with same was subjected to a transverse force the stabilizer would naturally tend to slide or or buckle since it is only connected to the ladder by a simple universal joint connection or the like near the platform of the step ladder. U.S. Pat. No. 3,901,354, issued to A. J. Grebausky, discloses another step ladder stabilizer which includes an extensible leg which is pivotally attached to a platform of a ladder. Once again, however, the spindly stabilizer element is only attached to the step ladder at one point so its strength and rigidity naturally suffer.
U.S. Pat. No. 3,878,917, issued to L. R. McBride, shows a similar stabilizer element for use with a "leanto" ladder as opposed to a step ladder. The McBride stabilizer, like the stabilizer discussed above, simply includes means for attaching the extensible stabilizer element to the apex of a ladder.
By contrast, the stabilizer disclosed in U.S. Pat. No. 3,508,628, issued to C. J. Conrad, includes a stabilizer element which is attached to the side rail or upright of a ladder at two points. This attachment scheme offers greater lateral strength and stability, but renders the stabilizer less adjustable. That is, the distance between the lower tip of the extensible stabilizer element and the ladder upright cannot be readily laterally adjusted depending on the ground conditions or the proximity of a wall or other impedient. Also, although the extensible stabilizer element of the Conrad stabilizer is attached at two points to the upright of a ladder, it is attached to only one of the ladder's uprights. Therefore, the stabilizer of conrad is not well braced against transverse loads or impacts; it will tend to move relative to the ladder uprights when subjected to a transverse load. Further, the Conrad stabilizer is not laterally adjustable, having only fully collapsed and fully extended lateral positions or states.
U.S. Pat. No. 3,786,900, issued to P. J. Olsen, discloses still another ladder stabilizer which is pivotally attached at its upper tip to the platform of a step ladder. The stabilizer element is also connected at its midpoint to the ladder. The element which attaches the midpoint of the stabilizer element to the ladder is transversely stabilized by a pair of elements which are attached to opposing side rails or uprights on the step ladder. This scheme provides some transverse and lateral strength and stability to the stabilizer element. However, the Olsen stabilizer is not laterally adjustable in a manner which allows it to accommodate various ground conditions. In addition, it is not transversely adjustable. A preferred stabilizer would possess lateral and transverse adjustability to accommodate a wide variety of ground conditions, while at the same time adequately bracing the ladder so that it will safely support an individual whose task necessitates moving about on the ladder and leaning to one side of the ladder or the other.
The ladder stabilizer of the present invention is directed to the shortcomings of prior art ladder stabilizers. In particular, it provides a laterally adjustable stabilizer which is sufficiently braced to provide sufficient lateral and transverse strength and stability to the ladder. A preferred embodiment includes an elongate stabilizer element which is also transversely adjustable. Lateral and transverse adjustment makes the ladder stabilizer useful irrespective of the environment in which the ladder must be used.